And I'm Melissa Block. New Hampshire voters are casting their ballots today in the first presidential primary of 2012. It's a crowded race that could become a little less so after tonight's results. Mitt Romney remains the favorite. He has been from the beginning. And NPR's Ari Shapiro joins us now from Romney headquarters in Manchester. Ari, Mitt Romney has been the frontrunner in New Hampshire for some time by a hefty margin. What's at stake in this vote tonight for him?

ARI SHAPIRO, BYLINE: Well, look, on the one hand, if he wins tonight, no matter how small the margin, it would make him the first non-incumbent Republican ever to win both Iowa and New Hampshire. That said, the campaign is hoping for, certainly, and in some way expecting him to come out head and shoulders above everybody else, which would help secure the air of inevitability that has surrounded him in this campaign. Romney has spent tons of time here in New Hampshire over the last five years.

He was governor of neighboring Massachusetts. He owns a house here. And here's what he told voters at his last rally before voting here last night in Manchester.

MITT ROMNEY: And so we come, you know, taught our little boys, little guys, how to ski here, went swimming here, taught them how to water ski on Lake Winnipesaukee. We've been coming here. We love the state.

SHAPIRO: So they're expecting a big win. But, Melissa, even if he does not secure a decisive win, this campaign has laid the infrastructure and set up the finances to go the distance, as evidenced by this morning. The campaign sent reporters a chart showing some of the states that vote in February and March and beyond and showing which candidates had registered to compete in those states. Not all of them have. And it shows that while this campaign is aiming for a quick, clean victory, they're ready for something that's a bit messier.

BLOCK: And Ari, much has been made of something that Mitt Romney said yesterday on the campaign trail, something his rivals have pounced on. Why don't you go through what he said and what the reaction has been?

SHAPIRO: Yeah, he was talking about health insurance companies and saying that if one charges too much or gives you bad service, you should be able to get a better one. But in making that point, he used the, perhaps, inapt phrase, I like being able to fire people, which everybody pounced on, took out of context and used it to portray him as sort of a cutthroat Wall Street coldhearted man who made a fortune off of firing other people.

The Romney campaign says, look, my record at Bain Capital was one of job creation, not job destruction. But the slip of the tongue on Romney's part brought about a last-minute cascade of attacks on him in the 24 hours before the final results come in here in New Hampshire.

BLOCK: Yeah. And let's take a minute, Ari, to focus on Mitt Romney's rivals in New Hampshire. Who is playing well with the voters there?

SHAPIRO: Well, you know, Jon Huntsman has staked his entire candidacy on a good performance in New Hampshire. He seems to be doing better than he was, but it's not clear whether that will be well enough to stay alive after tonight. Rick Santorum, who virtually tied Mitt Romney in Iowa, is trying to capitalize on the social conservative vote here, but that's less than half as large a population than they are in Iowa. You have Ron Paul, who's looking to independent voters, younger voters and libertarian voters.

They have a strong presence here in New Hampshire. And then, Newt Gingrich has been one of the loudest voices attacking Romney. He's been saying, look, if this guy's going to collapse under pressure, better that he do it now in the primary race than when he's face to face with President Obama in the general election. Then, the last guy still in the race you have is Rick Perry, who jumped right ahead from Iowa to South Carolina and is not competing here in New Hampshire tonight.

BLOCK: And Ari, you mentioned independent voters, the undeclared voters in New Hampshire, that's a hefty slice of the electorate. What do we know about the voters who are going to vote today in New Hampshire?

SHAPIRO: Well, as of yesterday, about half of them told pollsters they still hadn't made up their mind, so a surprise certainly is possible tonight. A typical New Hampshire voter is different from a typical Republican elsewhere in the state. They tend to be fiscally conservative, not so much socially conservative, very different from South Carolina, which votes next. Although, I should say that while South Carolina is very socially conservative, that's also a very pragmatic state where Republicans have chosen the ultimate nominee in every primary race going back to Reagan in 1980.

BLOCK: Okay. NPR's Ari Shapiro reporting from Mitt Romney's campaign headquarters in Manchester, New Hampshire. Ari, we'll be checking back in with you throughout the evening. Thank you so much. Transcript provided by NPR, Copyright NPR.